USED WRAPPERS

28 April 2000




USED WRAPPERS

NEED CLOSE CHECKS

With bale wrappers becoming

more sophisticated and more

expensive as a result, there

is decent demand for second-

hand machines. Peter Hill

enlisted the help of Berks

agricultural engineer

Paul Killen to highlight

what needs checking before

buying a used wrapper

BALE wrappers can come as simple or as sophisticated as you like. With basic manual controls using levers attached to hydraulic valves or with electro-hydraulic controls; tractor-mounted or trailed; with or without self-loading; and fully automatic for in-line operation behind the baler.

Whatever the design, there are fundamental components and systems that need to be checked before parting with cash for a used machine.

Before going as far as inspecting a potential buy, however, check that its hydraulic requirements are within the tractors capabilities. Wrappers do not demand a huge flow of hydraulic oil. But older tractors with tired hydraulics may not have sufficient resources to operate the machine at full speed.

The subject of this second-hand inspection, a Tanco Autowrap 1050 table wrapper, demands 20 litre/min, according to the spec sheet. It should then be capable of field wrapping between 25 and 30 bales an hour.

It has a loading cradle and in-cab electronic controls, and can wrap both round and square bales. This particular example has experienced a hefty workload, wrapping more than 21,000 bales over the past 30-months in the hands of Fawley, Berks-based contractor Paul Jannaway.

It looks a bit frayed at the edges and is in need of some pre-season repairs, he acknowledges. But he reckons it is still in perfectly serviceable order.

Giving such a machine the once over when parked up in a shed or farm-yard will be enough to form an opinion about its general condition and likely maintenance record.

But not enough to determine whether everything operates as it should. For that, the only option is to see it working – and preferably wrapping a bale, not just going through the motions.

Where to start? On a self-loading model such as this one, the bale lifting cradle is as good a place as any. For one thing, because they are prone to digging into the ground when the field surface is less than billiard table smooth. But also because enthusiastic operators who approach bales at speed have been known to mis-judge things and end up whacking the bale with the arm.

A bent and mis-aligned cradle that fails to pop bales on to the table correctly can result in wrapping problems – including the bale flying off if it does not sit centrally.

Metal fatigue

Heaving 0.5 tonne silage bales off the ground also takes its toll in terms of metal fatigue – so inspect welds for any sign of cracking, and pivot pins (which may be bushed) for damage or excessive wear.

The cross-member supporting the table tilt ram – which is used to tip wrapped bales off the table – is also worth checking for signs of stress, such as tiny cracks or paint work rippling in a distinctive fan-shaped pattern.

Clean rotation of the wrapping table or orbital arm carrying the film dispenser is clearly essential and for this, the hydraulic motor and any chain drives need to be in good order, including those that rotate the support rollers to turn the bale during the wrapping sequence.

These are subject to a fair bit of wear so should have been lubricated regularly. In any event, it is as well to replace the chains (and sprockets if worn) to avoid time-wasting break-downs during the season.

Rotating tables will be supported on either just a central bearing or, as in the case of the Tanco, on perimeter steel support rollers as well. These too need to rotate freely on a smooth deck – so its worth checking that they do and that the "floor" is free of any dimples caused by the table being lowered too hard from the tipped position.

Crucial assembly

The film hold and cut device is another crucial assembly that needs to work correctly to avoid problems. It holds the loose end of the film as the sequence begins, releases it as the bale continues to rotate, then cuts and holds the film ready for the next bale at the end of the process.

Whether operated by hydraulic ram or electrical actuator, check this device has not been bent by errant bales or gate posts, and that it operates as it should. A robust hard-wearing blade, adjustable to get a good shear-action, is preferable to a flimsier one that needs replacing too often.

Check the wrap dispenser itself for free-running rollers and a mounting post that is free of damage and fatigue cracks. It has to support a fair bit of weight as well as the drag of the stretch film as it is drawn out by the bale against the geared pre-stretch rollers.

The roller surface needs to be as near original as possible to maintain grip but may need a good clean to remove "tack" deposits from the sticky side of the plastic film.

A good look at hydraulic cylinders, hoses and valves should reveal any tell-tale oil leaks and, on machines with any sort of automated sequence, remember to check the control box and functions, and any mechanical trips or electrical proximity sensors.

Wrapper inspection check-list

Self-loading arm – look for signs of impact damage, misalignment and cracks indicating metal/weld fatigue.

Main frame – as above, especially around hydraulic cylinder mountings for self-loading arm and table tipping ram.

Pre-stretch unit – as above for the mounting post; check geared pre-stretch rollers run freely.

Controls – check for correct operation of hydraulic and solenoid valves, as well as Bowden cable and electro-hydraulic controls.

Hydraulics – as above for table or orbital arm motor; look for leaks from hoses and cylinders.

Drives – inspect chain and sprocket drives to table and table rollers for wear and damage. Also check table support rollers (if fitted) for free rotation. &#42

Above:Tanco Autowrap 1050 handles 1.2m round bales and square bales up to 0.8m wide. Any wrapper is best seen working to properly assess its condition and check that all functions are operating correctly.

Left: Load cradle can be damaged by the outer arm hitting a bale or gouging into the ground. This one has been modified with a telescopic section and hydraulic cylinder to adjust the spacing for different bales.

Above: Rippling paint is a give-away that repeatedly tipping heavy bales off the turntable is proving a bit too much for this mainframe cross member.

Above: Plain and bushed pivot pins (on loading and bale damper arms) can be damaged by impacts; check also for excessive wear.

Below: Chain and sprockets are prone to wear, as well as damage if allowed to run too slack. Removing guards can be fiddly but allows proper inspection.

Above: Table support rollers (where fitted) need to rotate freely on a reasonably smooth "floor". Accumulations of stretch film need to removed (a heated knife will help) to avoid damage to bearings.

Hydraulic motor and valves should be tucked out of harms way – but its worth uncovering them to check for correct operation and leaks.


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